The present invention relates to the field of torque limiting bolts and more particularly those having shear pins.
The use of members which shear upon the application of a predetermined torque to a bolt is old in the art. As stated in U.S. Pat. No. 4,167,886 issued to Seghezzi et al., a preset torque can be applied by means of a torque wrench. However, such wrenches are sensitive to damage and are otherwise deemed undesirable. This patent teaches positioning three shear pins between a bolt head cap and the bolt head interior. When the torque applied to the cap becomes excessive, the pins break and the cap becomes separated from the bolt head. Other similar devices which fracture employ hex nuts which shear off at the predetermined torque, thereby to eliminate the need for torque wrenches. However, these designs create broken off foreign objects which may be ingested or propelled by aircraft on the flight line, creating a dangerous condition. Such foreign objects in many other environments are also undesirable as they can cause falls for example.